The present invention relates generally to cooling towers, and more specifically, to an evaporative heat and mass exchanger with a coil module for evaporative closed circuit cooling or evaporative condensing.
In an induced draft cross flow or counter flow cooling tower, a fan is mounted in the roof outlet of the tower. This fan draws or induces airflow inwardly into the cooling tower through a side wall or opposite side walls of the tower. Water or other evaporative liquid to be cooled is pumped to the top of the cooling tower structure and distributed through a series of spray nozzles. These spray nozzles emit a diffuse spray of water across the top of a fill media. Such fill media typically comprises a bundle of spaced parallel plastic sheets across each of which the water spray is dispersed and downwardly passed by gravity. The large surface area across which the water is dispersed on such sheets leads to cooling by the induced air flow directed between the sheets. The cold water is collected in a sump and then passed through to the desired cooling system, wherein it will become heated and then pumped back to the cooling tower.
An indirect heat exchange unit is provided beneath the bundle of fill sheets. Such unit is typically comprised of serpentine heat exchange conduits or coils. The hot fluid to be cooled enters the heat exchange conduits through an inlet header at the lower or bottom edge of the conduits with the cool fluid exiting the conduits through a header joining the upper ends of the conduits. Alternately, a vapor to be condensed enters the top of the conduits and as it travels downwardly through the conduits becomes condensed and liquefied and exits the bottom header. One such cooling tower apparatus is shown in U.S. Pat. No. 4,683,101. The cooling is provided by sensible cooling from the spray water on the outside of the conduits. Cooling air may or may not flow through the indirect heat exchange unit.
On occasion, such as during cold weather months, it is desired to operate such cooling towers in a dry mode without the use of water or other fluids being sprayed downwardly across the fill direct heat exchange section. In such an arrangement, it would be desirable to open the sides of a cooling tower adjacent the indirect cooling section to inflow air. Such an arrangement would optimize the performance of the air-cooled, non evaporative heat exchanger.
Coil shed cooling towers are also known, which consist of a cooling tower with the direct evaporative heat exchanger with fill section located directly above a non-ventilated indirect cooling or coil section. Little to no cooling air is drawn through the indirect section. Such coil sheds have little to no cooling capacity when operated without the spray water flowing downwardly over the direct cooling or fill section. Such limitation on the operation of the tower limits the application and utility for such towers as they typically cannot be operated dry as during the winter months in cold climates. Further, the maximum wet mode performance of the coil or indirect section is limited as no air enters this section of the cooling tower. The design of the coil shed cooling tower is such that this section is closed to air inlet. In such an arrangement, it would be desirable to open the sides of a cooling tower adjacent the indirect cooling section to inflow air. Such an arrangement would optimize the performance of the air-cooled, non evaporative heat exchanger. Referring now to FIG. 3, which shows a section of the cooling tower of FIG. 1, a sliding cover 125 or removable panel is provided which can be moved to cover air inlet 149 or the fill inlet section 139. Cover 125 can be moved manually or by motor control.